Roofing shingle coating asphalts are usually produced by selecting a suitable feedstock asphalt and then processing that asphalt by air blowing to provide the properties desired for use in a coating asphalt. For example, asphalt feedstocks used to produce coating asphalts for roofing shingles are usually chosen so that they can be air-blown to: 1) raise their softening point so that they maintain their dimensions at high temperatures on a roof; 2) lower their penetration into a range where it allows proper press of granules without becoming too brittle; 3) raise their melt viscosity so that when filler is added the filled coating viscosity is in a range that allows a roofing shingle process to run at high speeds; and 4) create a shingle that will perform over many years on the roof in spite of being exposed to sun, high temperatures and rain.
Historically coating asphalt for roofing shingles has been produced by choosing a special grade of asphalt as the feedstock to the air blowing process in order to meet these properties. These special grades of asphalt were often materials that were softer (higher penetration, lower viscosity) than paving grade asphalt and were often called “roofer's flux”. In addition to being softer they needed to have high flash points to allow the final coating to be heated to high temperatures in preparation for mixing with filler and coating a glass fiber mat, and they needed to have the characteristics that once air blown to coating they exhibited excellent durability to weather. Unfortunately, these special grades of asphalt that can be air-blown to make coating asphalts are increasingly in short supply and therefore can be costly compared to many other types of asphalt, particularly commodity paving asphalts. A new process that increases material opportunities in the production of roofing shingle coating asphalt would be beneficial to the asphalt roofing product business.